Direct and indirect emissions of CO₂


EN16Greenhouse-gas emissions connected with Terna’s activities are caused by:

  • direct consumption of energy sources (gasoline and gas oil for vehicles, gas oil for generating sets and heating and methane for heating);
  • indirect consumption of energy sources (electricity consumption);
  • leaks of SF6 (sulfur hexafluoride), a greenhouse gas used in station equipment for its high insulating power;
  • leaks connected to R22 refrigerant gas, used in air conditioners.


Leakage of SF6 is the main direct source of Terna’s greenhouse-gas emissions. From 2009 to 2011, the quantity of SF6 present in Terna’s plants increased by 77 tons (+23%). This trend is common to many transmission companies and is bound to continue in the near future because of technical reasons connected with the higher insulating performance of the gas and the reduced encumbrance of stations constructed with equipment containing SF6 with respect to more traditional solutions. For this reason, the indicator that Terna considers is the percentage of leakage compared to the total quantity of gas contained in the equipment.



Direct emissions      
SF6 leakage (2) 57,406 60,313 68,522
R22 leakage (2) 25 240 1,104
Gasoline for vehicles 520 493 483

Gas oil for vehicles

5,605 5,520 5,368
Methane for heating 531 408 344
Gas oil for generating sets and heating 836 954 983
Total direct emissions (2) 64,922 67,928 76,805
Indirect emissions      
Electricity (3) 71,463 70,692 66,306
Total direct and indirect emissions (2) 136,385 138,620 143,111
(1) The conversion of direct consumption into emissions of CO2 equivalent is made using the parameters specified by the Greenhouse Gas Protocol (GHG) Initiative. For indirect consumption of electricity, the conversion is made taking into account the weight of thermoelectric production in total Italian electricity in 2011. The reference for the breakdown of the production mix is the “Monthly report on the electricity system” for December 2011, which is available online at (2) From this year, with respect to direct emissions it was decided to report the amount of the leakage associated with the consumption of R22 (value previously included in the text). The data was also included in 2010-2009. As of this year, IPCC AR 4 conversion factors have been used, which brought about a variation of tons of SF6 and R22 equivalent with respect to what had been previously published. The two above-mentioned variations consequently led to a variation in total direct and indirect emissions with respect to those previously published. (3) Throughout 2011, surveying and in-depth investigation on electricity consumption to supply stations and offices were carried out. In light of the results of said activity, also data from 2009-2010 was reviewed downward, which were found to be over-estimated. Consequently, also the total emissions data has been modified.

CO2 emissions: comparative data

Comparison between Terna and other companies on the subject of greenhouse gas emissions takes as a reference the total of direct and indirect emissions in thousands of tons of CO2 equivalent.

Both the data from transmission companies (TSO panel) and the data from large Italian listed companies (FTSE-MIB) as well as from international leaders in sustainability (SAM - Supersector Leaders) were examined.

The data in absolute value are not representative of company performance concerning the efficient use of energy and the containment of climate altering emissions, which should be evaluated over time and with reference to normalization factors that eliminate the differences stemming from the different type of activities and the size of the company.

In the absence of normalization factors that are significant and valid for all sectors, it was decided that it would nevertheless be of interest - despite the limited comparability - to present company data on CO2 emissions in absolute values. Said data, which according to the case takes on very different orders of magnitude, provides at least an indication on the relevance of greenhouse gas emissions - therefore of the materiality of their reduction in terms of sustainability – in different sectors and in different companies.

For example, within the TSOs, the highest data refers to Eskom, which operates in South Africa and which, among its activities, counts also the generation of electricity, whereas the lowest data refers to TDE, a small-sized TSO that operates in Bolivia and that works only in the field of electricity transmission.   

In 2011, greenhouse gas emissions linked to Terna’s activities totaled 136.4 thousands of tons of CO2 equivalent; in 2010, for which comparison data is available, emissions 138.6 thousands of tons of CO2 equivalent. 

TSO Panel: 16 available data; average CO2 emissions: 25,938.9 thousand tons CO2; lowest figure: 0.8 (TDE - Bolivia); highest figure: 230,300 (Eskom - South Africa). In this comparison, Terna ranked below the average, which is the highest among the averages of the three panels and is influenced by four transmission operators that also have electricity generation activities. The lowest figure refers to the smallest operator out of all those considered.

FTSE-MIB Panel: 18 available data; average CO2 emissions: 10,802.5 thousand tons CO2; lowest figure: 15.1 (Ubi Banca); highest figure: 116,645.0 (Enel). Terna ranked among the major Italian companies with the fewest emissions, well below the average and with total emissions just above those of banks and insurance companies which registered the lowest values.

SAM - Supersector Leaders Panel: 18 available data; average CO2 emissions: 13,647.8 thousand tons CO2; lowest figure: 34.2 (Itausa - Financial Services); highest figure: 146,274.0 (Stockland - Real Estate). Also in comparison with the global best practices of sustainability, Terna confirmed a quantity of emissions well below the average. The high standard deviation points to great variability among sectors, some of which are characterized by high quantities of CO2 (for example, companies from the Oil & Gas sector).

The great variability of company data renders a graphic illustration of little importance; the table shows the lowest, average and highest figures of the three panels.

Greenhouse gas emissions – thousands of tons CO2 - 2010
TSO FTSE-MIB SAM - Supersector Leaders
Average 25,938.9 10,802.5 13,647.8
Max 230,300.0 116,645.0 146,274.0
Min 0.8 15.1 34.2
Standard Dev. 63,799.6 30,159.0 35,703.4
Terna 138.6